Projection system

ABSTRACT

A projection system including at least a light source, at least a dichroic filter element and a light-adjusting diaphragm element is provided. The light source is configured to emit a first color light having a spectrum of a first wavelength range and a second color light having a spectrum of a second wavelength range. The dichroic filter element is configured to reflect or allow the first color light and the second color light to pass through. The light-adjusting diaphragm element has a filter and is located on an optical path generated after the first color light and the second color light are split. The first color light passes through the filter, which blocks at least a part of the energy of the second color light, such that a transmittance of the spectrum of the first wavelength range is greater than that of the spectrum of the second wavelength range.

This application claims the benefit of People's Republic of Chinaapplication Serial No. 201910971955.4, filed Oct. 14, 2019, the subjectmatter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates in general to a projection system, and moreparticularly to a projection system having a light-adjusting diaphragmelement.

Description of the Related Art

In response to the current trend of lightweight, slimness andcompactness, conventional projectors are directed towardsminiaturization and high color performance. Micro-projectors havinggreat portability can be manufactured as portable micro-projectors, andcan further be used in various electronic products. For example,micro-projectors can be built in electronic products, such as mobilephones, multi-media layers or notebook computers, to expand theirfunctional diversity.

Optical elements, such as diaphragm and lens, can be used in aprojection system to adjust the light of the light-emitting element. Thediaphragm, for example, can be a digital micro-mirror device (DMD) or aliquid crystal switch element. To achieve a high optical performance inbrightness, most of the current micro-projectors use the light-emittingdiodes of the three primary colors, namely, red, green and blue, as thelight source, and directly project the tri-color lights to the digitalmicro-mirror device to form an image.

In terms of contrast detection, human eyes are most sensitive to thegreen light. The green pattern looks brighter and provides a bettercontrast effect. However, during contrast detection, if the brightnessof a stray light is too high, the stray light will affect the overallcontrast of the output image, making it difficult to improve the imagequality of the projection system. Meanwhile, since the color gamut ofthe image becomes smaller, the requirement of wide color gamut accordingto the DCI-P3 color gamut standards cannot be met.

SUMMARY OF THE INVENTION

The invention is directed to a projection system capable of reducing thedark field brightness of the image to increase the image contrastwithout affecting the color performance of the image.

According to one embodiment of the present invention, a projectionsystem is provided. The projection system includes at least a lightsource, at least a dichroic filter element and a light-adjustingdiaphragm element. The light source is configured to emit a first colorlight having a spectrum of a first wavelength range and a second colorlight having a spectrum of a second wavelength range. The dichroicfilter element is configured to reflect or allow the first color lightand the second color light to pass through. The light-adjustingdiaphragm element has a filter and is located on an optical pathgenerated after the first color light and the second color light arecombined, wherein the first color light passes through the filter, whichblocks at least a part of the energy of the second color light, suchthat a transmittance of the spectrum of the first wavelength range isgreater than a transmittance of the spectrum of the second wavelengthrange.

According to another embodiment of the present invention, a projectionsystem is provided. The projection system includes a first light source,a second light source, a light-combining prism element and alight-adjusting diaphragm element. The first light source is configuredto emit a first color light having a spectrum of a first wavelengthrange; the second light source is configured to emit a second colorlight having a spectrum of a second wavelength range. Thelight-combining prism element is located on an optical path of the firstlight source and the second light source to combine the first colorlight and the second color light. The light-adjusting diaphragm elementis interposed between the second light source and the light-combiningprism element and has a filter, which blocks at least a part of theenergy of the second color light, such that a transmittance of thespectrum of the second wavelength range is less than a set value.

The above and other aspects of the invention will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment(s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B respectively are schematic diagrams of a transmittanceof the spectrum of each color light.

FIG. 2A is a schematic diagram of a projection system having alight-combining prism element according to an embodiment of the presentinvention.

FIG. 2B is a schematic diagram of a projection system having a dichroicfilter element according to an embodiment of the present invention.

FIGS. 3A and 3B are schematic diagrams of a projection system accordingto two embodiments of the present invention.

FIG. 4A is a schematic diagram of a light-adjusting diaphragm element ofa projection system according to an embodiment of the present invention.

FIGS. 4B and 4C respectively are schematic diagrams of a light-adjustingdiaphragm element of a projection system according to another embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Detailed descriptions of the invention are disclosed below with a numberof embodiments. However, the disclosed embodiments are for explanatoryand exemplary purposes only, not for limiting the scope of protection ofthe invention. Similar/identical designations are used to indicatesimilar/identical elements. Directional terms such as above, under,left, right, front or back are used in the following embodiments toindicate the directions of the accompanying drawings, not for limitingthe present invention.

According to an embodiment of the present invention, a projection systemconfigured to project an image light on a screen is provided. Generallyspeaking, contrast refers to a ratio of the brightness of a whiteprojection image to the brightness of a black projection image projectedor a ratio of the brightness of a white block in a black and whiteinterval image to the brightness of a black block in the black and whiteinterval image. To increase the image contrast, a light-adjustingdiaphragm element 140 (refer to FIGS. 2A and 2B) can be located on theoptical path generated after the lights are combined or split to reducethe amount of the light entering the projection system 100 and make thedark field of the projection image becomes darker, such that thecontrast and graduation of the image can be increased.

Referring to FIGS. 1A and 1B, schematic diagrams of a transmittance ofthe spectrum of each color light are respectively shown. The lightsource is configured to emit a first color light having spectrum Wr orWb of a first wavelength range and a second color light having aspectrum Wg of a second wavelength range. In an embodiment, the firstcolor light having the spectrum Wr or Wb can pass through the lightfiltering material f1, but at least a part of the energy of the secondcolor light is blocked by the light filtering material f1, such that thetransmittance of the spectrum Wr or Wb of the first wavelength range isgreater than the transmittance of the spectrum Wg of the secondwavelength range.

In an embodiment, the spectrums Wr and Wb of the first wavelength rangerefer to the blue light spectrum and the red light spectrum, and thespectrum Wg of the second wavelength range refers to the green lightspectrum or the yellow light spectrum (495-570 nm or 570-590 nm). Theblue light spectrum and the red light spectrum of the first wavelengthrange can pass through the filter 143 of the light-adjusting diaphragmelement 140; the energy of the yellow light spectrum or the green lightspectrum of the second wavelength range can be blocked by the filter 143and become eliminated. Since the blue light spectrum and the red lightspectrum will not be blocked by the filter 143, the output energy of theblue light spectrum and the red light spectrum will not decrease. Theprojection system 100 of the present invention can eliminate the energyof other light spectrum, therefore it is not limited to eliminate theenergy of the green light spectrum and the yellow light spectrum.

Refer to FIG. 2A. In an embodiment, the projection system 100 includes aplurality of light sources 110, a light-combining prism element 101 anda light-adjusting diaphragm element 140. The light source 110, forexample, can be a light-emitting element, such as light-emitting diode,laser diode, metal halogen bulb, UHE bulb or UHP bulb, and can be usedto emit the color lights of distinct wavelength ranges for illuminationor optical projection. The light-combining prism element 101 has asemi-reflective/semi-penetration coating film configured to reflect orallow the color lights of distinct wavelength ranges to pass through.For example, the blue light Lb and the red light Lr both correspond tothe first wavelength range, and can be reflected to the light-adjustingdiaphragm element 140 by the light-combining prism element 101; thegreen light Lg or the yellow light corresponds to the second wavelengthrange, and can pass through the light-combining prism element 101 toreach the light-adjusting diaphragm element 140. Additionally, thelight-adjusting diaphragm element 140 is located on the optical pathgenerated after the blue light, the red light and the green light (thatis, the first color light and the second color light) are combined toadjust the output energy of the green light or the yellow light(represented by Lg′). In another embodiment, the light-adjustingdiaphragm element 140 can be interposed between the light source 110emitting the green light and the light-combining prism element 101 toadjust the output energy of the green light, such that the transmittanceof the green light spectrum Wg (the spectrum corresponding to the secondwavelength range) is less than a set value.

Refer to FIG. 2B. In an embodiment, the projection system 100 includes alight source 110, at least a dichroic filter element 102 and alight-adjusting diaphragm element 140. The light source 110 isconfigured to emit a white light. The dichroic filter element 102 isconfigured to divide the white light into multiple color lights Lr, Lb,and Lg. The dichroic filter element 102 has a multi-color coating filmconfigured to reflect or allow the color lights of distinct wavelengthranges to pass through. For example, the blue light Lb and the red lightLr corresponding to the first wavelength range can respectively passthrough one of two dichroic filter elements 102; the green light Lg orthe yellow light corresponding to the second wavelength range cansequentially be reflected to the light-adjusting diaphragm element 140by the two dichroic filter elements 102. The light-adjusting diaphragmelement 140 is located on the optical path generated after the bluelight, the red light and the green light (that is, the first color lightand the second color light) are split to adjust the output energy of thegreen light or the yellow light (Lg′ represents the adjusted Lg).

Also, the color lights emitted by the light source 110 can be adjustedby an optical element indicated in FIGS. 3A and 3B, such as a colorwheel, a light tube, a set of lens, a total internal reflection (TIR)prism, a lens having diopter (such as field lens) or a diaphragm, andthe detail of description are not repeated here.

The diaphragm can be a digital micro-mirror device (DMD), a liquidcrystal switch element or any electricity-driven element or devicecapable of converting the light emitted by the light-emitting elementinto an image light. The diaphragm is commonly used in the digitalprojection system.

The light-adjusting diaphragm element can be disposed behind the lens tolimit the diameter of the light beam passing through the lens. Generallyspeaking, the diaphragm can eliminate the peripheral energy of theincident light to avoid the peripheral energy being too high andaffecting the contrast. Refer to FIGS. 3A and 3B. The projection system100 of the present invention can have a light-adjusting diaphragmelement 141 disposed on a suitable optical path to purify the imagelight and increase the color performance of the image light.

The projection system 100 includes a light source 110, a filter device112, a light tube 114, at least a condenser 116, a reflector 118, adigital micro-mirror device 120, a projection lens 130 and alight-adjusting diaphragm element 141. The light-adjusting diaphragmelement 141 is interposed between the light source 110 and theprojection lens 130. The light-adjusting diaphragm element 141 can belocated at position A of FIG. 3A or position B of FIG. 3B. In anembodiment, the light tube 114 is interposed between the light source110 and the projection lens 130 to limit the color light L travellingtowards the projection lens 130 through the optical path. The condenser116 is interposed between the light tube 114 and the digitalmicro-mirror device 120. The reflector 118 is interposed between thecondenser 116 and the digital micro-mirror device 120 to reflect thecolor light L to the digital micro-mirror device 120.

The digital micro-mirror device 120, located on the optical pathgenerated after all color lights L are combined, includes a plurality ofmicro-reflectors (not illustrated) whose angles are adjustable. Themicro-reflector is configured to reflect the color light L to theprojection lens 130 to become an image light, or adjust the angle of themicro-reflector to reflect the color light L to the dark state opticalpath instead of outputting the image light. The light-adjustingdiaphragm element 141 is disposed on the diaphragm behind the light tube114, that is, the diaphragm interposed between the light tube 114 andthe projection lens 130. As indicated in FIG. 3A, the light-adjustingdiaphragm element 141 is located on the position interposed between thelight tube 114 and the reflector 118 or is located on the positioninterposed between two condensers 116. Or, as indicated in FIG. 3B, thelight-adjusting diaphragm element 141 is located on the positioninterposed between the digital micro-mirror device 120 and theprojection lens 130.

Refer to FIG. 4A, the light-adjusting diaphragm element 140 has a filter143 whose periphery has an opaque light-shielding region 144. Thelight-adjusting diaphragm element 140 is formed of an entire filterelement, and is shielded to form the light-shielding region 144. Forexample, the light-shielding region 144 is formed of an opaque material,such as black matt paint, by way of coating, evaporation or adhesion.

In an embodiment, the filter 143 can be formed of a light filteringmaterial having distinct transmittances with respect to the green lightor the yellow light. Refer to FIG. 1B. The first light filteringmaterial f1 has a first transmittance with respect to the green light orthe yellow light; the second light filtering material f2 has a secondtransmittance with respect to the green light or the yellow light; thethird light filtering material f3 has a third transmittance with respectto the green light or the yellow light. The first transmittance issmaller than the second transmittance; the second transmittance issmaller than third transmittance. In the present embodiment, the lightfiltering materials f1, f2, and f3 having distinct transmittances canrespectively be disposed on the filter 140, such that the transmittanceof the spectrum Wg of the green light or the yellow light graduallydecreases or increases outwards from the center of the filter 140. Forexample, the transmittance decreases to 70% from 100%, and then furtherdecreases to 50%, 20% or 0% from 70%.

Refer to FIG. 4B. The center of the light-adjusting diaphragm element140 has an opening 142. The opening 142 has a circular shape or othershape and allows all color lights to completely pass through, such thatthe output energy of the central region of the diaphragm can beincreased. In an embodiment, the light-adjusting diaphragm element 140is an opaque metal element, and a hole is formed on the opaque metalelement by way of stamping. Then, the filter 143 is embedded into thehole. The center of the filter 143 forms an opening 142, which allowsthe color light to completely pass through. The opening 142 can beformed by hollowing the filter 143 or by using a transparent material.

Refer to FIG. 4C. The filter 143 is located at the center of thelight-adjusting diaphragm element 140. The periphery of the filter 143has an opening 142 formed of a transparent material. The opening 142 hasa circular shape, oval shape or other shape, and allows the color lightsurrounding the filter 143 to completely pass through, such that theoutput energy of the periphery of the diaphragm can be increased. Theopening 142, which can be formed by hollowing the light-adjustingdiaphragm element 140, connects the filter 143 and the opaque region 144in a radial direction.

The function of the light-adjusting diaphragm element 140 is similar tothe combination of a diaphragm and a filter. The first color light (theblue light spectrum Wb and the red light spectrums Wr corresponding tothe first wavelength range) can pass through the filter 143 or theopening 142 of the light-adjusting diaphragm element 140, and at least apart of the energy of the second color light (the yellow light spectrumor the green light spectrum Wg corresponding to the second wavelengthrange) is blocked by the filter 143 or at least a part of the energypasses through the opening 142, such that a transmittance of thespectrum of the first wavelength range is greater than a transmittanceof the spectrum of the second wavelength range. Thus, the projectionsystem 100 disclosed in above embodiments of the present invention canreduce the dark field brightness to increase the image contrast withoutaffecting the color performance of the image.

Meanwhile, during contrast detection, since the brightness of the straylight decrease, the overall contrast of the output image will relativelyincrease and the image quality of the projection system will improve.Meanwhile, since the color gamut of the image is purified by thelight-adjusting diaphragm element, the requirement of wide color gamutaccording to the DCI-P3 color gamut standard can be met.

While the invention has been described by way of example and in terms ofthe preferred embodiment(s), it is to be understood that the inventionis not limited thereto. On the contrary, it is intended to cover variousmodifications and similar arrangements and procedures, and the scope ofthe appended claims therefore should be accorded the broadestinterpretation so as to encompass all such modifications and similararrangements and procedures.

What is claimed is:
 1. A projection system, comprising: at least a lightsource configured to emit a first color light having a spectrum of afirst wavelength range and a second color light having a spectrum of asecond wavelength range; at least a dichroic filter element configuredto reflect or allow the first color light and the second color light topass through; and a light-adjusting diaphragm element having a filterand located on an optical path generated after the first color light andthe second color light are split by the dichroic filter element, whereinthe first color light passes through the filter, and the filter blocks apart of the energy of the second color light, such that a transmittanceof the spectrum of the first wavelength range is greater than atransmittance of the spectrum of the second wavelength range.
 2. Theprojection system according to claim 1, wherein a center of thelight-adjusting diaphragm element has an opening, and the filter islocated on an outer edge of the opening.
 3. The projection systemaccording to claim 2, wherein the filter is hollowed to form the openingor the opening is formed of a transparent material.
 4. The projectionsystem according to claim 1, wherein the filter is located at a centerof the light-adjusting diaphragm element, the light-adjusting diaphragmelement has an opening located on an outer edge of the filter.
 5. Theprojection system according to claim 4, wherein the filter is hollowedto form the opening or the opening is formed of a transparent material.6. The projection system according to claim 1, wherein thelight-adjusting diaphragm element is formed of an entire filter element,and the peripheral area of the filter is shielded to form alight-shielding region.
 7. The projection system according to claim 1,wherein the transmittance of the spectrum of the second wavelength rangediminishes outwards from a center of the filter.
 8. The projectionsystem according to claim 7, wherein the filter is formed of lightfiltering materials having distinct transmittances with respect to thesecond color light.
 9. The projection system according to claim 1,further comprising a digital micro-mirror device located on an opticalpath generated after the first color light and the second color lightare combined.
 10. The projection system according to claim 9, furthercomprising at least a condenser and a reflector, the reflector isinterposed between the condenser and the digital micro-mirror device toreflect the first color light and the second color light to a pluralityof micro-reflectors of the digital micro-mirror device.
 11. A projectionsystem, comprising: a first light source configured to emit a firstcolor light having a spectrum of a first wavelength range; a secondlight source configured to emit a second color light having a spectrumof a second wavelength range; a light-combining prism element located onan optical path of the first light source and the second light source tocombine the first color light and the second color light; and alight-adjusting diaphragm element having a filter and located on anoptical path generated after the first color light and the second colorlight are combined by the light-combining prism element or interposedbetween the second light source and the light-combining prism element,wherein a part of the energy of the second color light is blocked by thefilter, such that a transmittance of the spectrum of the secondwavelength range is less than a set value.
 12. The projection systemaccording to claim 11, wherein the center of the light-adjustingdiaphragm element has an opening, and the filter is located on an outeredge of the opening.
 13. The projection system according to claim 12,wherein the filter is hollowed to form the opening or the opening isformed of a transparent material.
 14. The projection system according toclaim 11, wherein the filter is located at the center of thelight-adjusting diaphragm element, and the light-adjusting diaphragmelement has an opening located on an outer edge of the filter.
 15. Theprojection system according to claim 14, wherein the filter is hollowedto form the opening or the opening is formed of a transparent material.16. The projection system according to claim 11, wherein thelight-adjusting diaphragm element is formed of an entire filter element,and a peripheral area of the filter is shielded to form alight-shielding region.
 17. The projection system according to claim 11,wherein the transmittance of the spectrum of the second wavelength rangediminishes outwards from a center of the filter.
 18. The projectionsystem according to claim 17, wherein the filter is formed of lightfiltering materials having distinct transmittances with respect to thesecond color light.
 19. The projection system according to claim 11,further comprising a digital micro-mirror device located on an opticalpath generated after the first color light and the second color lightare combined.
 20. The projection system according to claim 19, furthercomprising at least a condenser and a reflector, the reflector isinterposed between the condenser and the digital micro-mirror device toreflect the first color light and the second color light to a pluralityof micro-reflectors of the digital micro-mirror device.